Potential agrifood application of seriguela (Spondias purpurea L.) residues extract and nanoZnO as antimicrobial, antipathogenic and antivirulence agents

The impact of phytopathogenic microorganisms in several crops causes significant losses in agrifood industry, spoilage throughout food chain and storage. Nanoparticles and plant extracts have been highlighted by their antimicrobial properties applied in food packaging, agriculture, drug delivery systems and other medical approaches. Over the past few years, this group have studied the application of ZnO nanoparticles and agroindustrial wastes in edible food coatings/films. This study aimed to evaluate active characteristics from the extract of seriguela processing wastes and nanoZnO regarding to their inhibitory activity against bacterial pathogenicity and virulence systems TTSS (Type Three Secretion System) and QS (Quorum Sensing) for Pseudomonas savastanoi. Also, antibacterial action (inhibition area) against species of Curtobacterium, Clavibacter, E. coli, Xanthomonas and Serratia, and antifungal against Botrytis cinerea (reduction in colony size). The 60% extract inhibited the activation of QS and TTSS system in 20.26% and 13.54%, respectively; while nanoZnO at 3% reduced 46.77% QS and increased 302.88% TTSS. Extract without dilution inhibited the growth of Clavibacter michiganensis pv michiganensis (Gram-positive) and Xanthomonas phaseoli (Gram-negative), inhibitory zone of 94.25 mm2 and 452.39 mm2 respectively. The latter also being inhibited by nanoZnO 1 and 2% (138.23 mm2) and 3% (275.67 mm2). Pure extract inhibited 17.38% growth of fungal colony and nanoZnO (1 and 3%) in 33.08%. Finally, the active agents studied showed to be promising in the prevention of phytopathogenic diseases and consequently economic losses, food films/coatings and the extract as a biopesticide, reducing the environmental impact.

In-Depth Analysis of the Role of the Acinetobactin Cluster in the Virulence of Acinetobacter baumannii

Acinetobacter baumannii is a multidrug-resistant pathogen that represents a serious threat to global health. A. baumannii possesses a wide range of virulence factors that contribute to the bacterial pathogenicity. Among them, the siderophore acinetobactin is one of the most important, being essential for the development of the infection. In this study we performed an in-depth analysis of the acinetobactin cluster in the strain A. baumannii ATCC 17978. For this purpose, nineteen individual isogenic mutant strains were generated, and further phenotypical analysis were performed. Individual mutants lacking the biosynthetic genes entA, basG, basC, basD, and basB showed a significant loss in virulence, due to the disruption in the acinetobactin production. Similarly, the gene bauA, coding for the acinetobactin receptor, was also found to be crucial for the bacterial pathogenesis. In addition, the analysis of the ΔbasJ/ΔfbsB double mutant strain demonstrated the high level of genetic redundancy between siderophores where the role of specific genes of the acinetobactin cluster can be fulfilled by their fimsbactin redundant genes. Overall, this study highlights the essential role of entA, basG, basC, basD, basB and bauA in the pathogenicity of A. baumannii and provides potential therapeutic targets for the design of new antivirulence agents against this microorganism.

Discovery of uncompetitive inhibitors of SapM that compromise intracellular survival of Mycobacterium tuberculosis

SapM is a secreted virulence factor from Mycobacterium tuberculosis critical for pathogen survival and persistence inside the host. Its full potential as a target for tuberculosis treatment has not yet been exploited because of the lack of potent inhibitors available. By screening over 1500 small molecules, we have identified new potent and selective inhibitors of SapM with an uncompetitive mechanism of inhibition. The best inhibitors share a trihydroxy-benzene moiety essential for activity. Importantly, the inhibitors significantly reduce mycobacterial burden in infected human macrophages at 1 µM, and they are selective with respect to other mycobacterial and human phosphatases. The best inhibitor also reduces intracellular burden of Francisella tularensis, which secretes the virulence factor AcpA, a homologue of SapM, with the same mechanism of catalysis and inhibition. Our findings demonstrate that inhibition of SapM with small molecule inhibitors is efficient in reducing intracellular mycobacterial survival in host macrophages and confirm SapM as a potential therapeutic target. These initial compounds have favourable physico-chemical properties and provide a basis for exploration towards the development of new tuberculosis treatments. The efficacy of a SapM inhibitor in reducing Francisella tularensis intracellular burden suggests the potential for developing broad-spectrum antivirulence agents to treat microbial infections.

Old Problems and New Solutions: Antibiotic Alternatives in Food Animal Production

The antimicrobial resistance crisis is a Global Health challenge that impacts humans, animals, and the environment alike. In response to increased demands for animal protein and by-products, there has been a substantial increase in the use of antimicrobial agents in the animal industry. Indeed, they are extensively used to prevent, control, and/or treat disease in animals. In addition to infection control, in-feed supplementation with antimicrobials became common practice for growth promotion of livestock. Unfortunately, the global overuse of antimicrobials has contributed to the emergence and spread of resistance. As such, many countries have implemented policies and approaches to eliminate the use of antimicrobials as growth promoters in food animals, which necessitates the need for alternate and One Health strategies to maintain animal health and welfare. This review summarizes the antimicrobial resistance crisis from Global Health and One Health perspectives. In addition, we outline examples of potential alternate strategies to circumvent antimicrobial use in animal husbandry practices, including antivirulence agents, bacteriophages, and nutritional measures to control bacterial pathogens. Overall, these alternate strategies require further research and development efforts, including assessment of efficacy and the associated development, manufacturing, and labor costs.

Nanolipoidal α-terpineol modulates quorum sensing regulated virulence and biofilm formation in Pseudomonas aeruginosa

Aim: Pseudomonas aeruginosa has emerged as a major opportunistic pathogen meaning there is an immediate need to develop efficient antivirulence agents which offer a new class of superior therapeutics. Methods: Nanostructured lipid carriers (NLCs) containing α-terpineol (αT) were developed and characterized to determine expression profiles of quorum sensing regulated genes, antivirulence activity and antibiofilm effects against P. aeruginosa. Results: The αT-NLCs had a size of 145.4 nm, polydispersity index of 0.242 and ζ-potential of -31.4 mV. They exhibited pronounced effects on the inhibition of quorum sensing mediated virulence and biofilm formation which were confirmed by molecular docking analysis and gene expression profiles. Conclusion: αT-NLCs show promise as effective antivirulence agents against P. aeruginosa in the postantibiotic era.